There are many devices that require a relatively strong, uniform magnetic field. For example, magnetic resonant imaging devices, power tubes for radars, and other known devices that utilize a relatively strong, uniform magnetic field. Many of these permanent permanent magnet structures provide a relatively high uniform magnetic field and have embodied the principles of a "magic" ring, cylinder, hemisphere, or sphere. For example, several permanent magnet structures of this type are disclosed in U.S. Pat. No. 5,216,401 issuing Jun. 1, 1993 to Leupold and entitled "Magnetic Field Sources Having Non-Distorting Access Ports", which is herein incorporated by reference. Therein disclosed is a permanent magnet structure having a shell of magnetic material and a hollow cavity. The shell is permanently magnetized to produce a substantially uniform magnetic field in the cavity. The magnetization of the shell is the result of two magnetization components. Another example is U.S. Pat. No. 4,835,506 issuing May 30, 1989 to Leupold and entitled "Hollow Substantially Hemispherical Permanent Magnet High Field Flex Source", which is herein incorporated by reference. Therein disclosed is a hollow hemispherical flex source which produces a uniform high magnetic field in its central cavity. The hemispherical permanent magnet structure is comprised of a plurality of wedge shaped portions having multiple sections with each section having a defined magnetic orientation.
Additionally, there have been manufacturing methods developed in an attempt to manufacture more easily these relatively complex permanent magnet structures. A method of manufacturing a magic ring or a cylinder is disclosed in U.S. Statutory Invention Registration H591 published Mar. 7, 1989, issuing to Leupold and entitled "Method of Manufacturing of a Magic Ring", which is herein incorporated by reference. Therein disclosed is a method of making a permanent magnet cylindrical structure made from magnetically hard material which provides a relatively intense uniform magnetic field within a central working space. The cylinder is cut into sections and then opposing pairs of sections are interchanged to form the desired magnetic orientation. Another method of making permanent magnet cylindrical and spherical structures is disclosed in U.S. Pat. No. 5,337,472 issued Aug. 16, 1994 to Leupold and McLane and entitled "Method of Making Cylindrical and Spherical Permanent Magnet Structures", which is herein incorporated by reference. Therein disclosed are methods of manufacturing rings, cylinders, hemispheres, and spheres having a relatively strong central magnetic field. A method is disclosed of making a hemispherical or spherical permanent magnet structure by cutting wedge or melon shaped portions into sections, rotating the sections about a radial axis prior to magnetization, magnetizing the sections in a uniform magnetic field, rotating the magnetic sections into their original positions, thereby forming the resultant desired permanent magnet structure. Additionally disclosed is the method of rearranging sections in order to obtain a desired magnetic orientation.
While many of these permanent magnet structures are desirable, they are often difficult to manufacture. Additionally, while the above described methods facilitate the manufacturing of these relatively complicated permanent magnet structures, the above methods do not lend themselves to mass production. Therefore, as these relatively complex permanent magnet structures become more widely used and incorporated into more devises, there is a need for developing manufacturing methods that are suitable for mass production, including permitting relatively easy and inexpensive manufacture of these relatively complex permanent magnet structures.